Researchers leading a large-scale human study of an experimental anticlotting drug being developed by DuPont Co. said they are moving forward with the trial despite the recent failure of four similar compounds in other studies.

The decision comes in the wake of an announcement last week that SmithKline Beecham PLC halted a major study of its drug lotrafiban because an interim safety check revealed more deaths than expected among patients getting the drug compared with those getting a placebo. Based in part on those findings,...